Life duration/habit: Leafy spurge is an aggressive, persistent, deep-rooted perennial, growing to a height of 1 meter (3 ft) or taller. Vegetative stems manufacture sugars for root reserves while other stems produce flowers.

Reproduction: Leafy spurge reproduces by vegetative re-growth from spreading roots and by the production of large quantities of seeds that are often dispersed by birds, wildlife, humans, and in rivers and streams.

Roots: Leafy spurge roots are brown with pinkish buds. Plants are able to maintain high root reserves through an extensive root system, ranging from a massive network of small lateral roots near the soil surface [within 30.5 cm (12 in)] to deep, penetrating taproots that may extend to depths of 3 to 7 meters (9 to 21 ft). This ability to maintain high root reserves permits the plant to recover quickly from physical and most chemical damage.

Stems and leaves: The stems are thickly clustered and bear narrow, 2.5 to 10 cm (1 to 4 in) long leaves that are alternately arranged along the stems. When damaged, leaves and stems produce a milky latex.

Flowers: The small flowers are yellowish-green, arranged in clusters, and enclosed in yellow-green bracts.

Fruits and seeds: Seeds are oblong, gray to purple, and occur in clusters of three. When dry, the seed capsules shatter, scattering seeds away from the plant.

Impact: Leafy spurge produces a milky latex that is poisonous to some animals and can cause blistering and irritation on skin. The digestive tract is similarly affected when this plant is eaten by humans and some animals. In cattle it causes scours and weakness. When ingested in larger amounts it can cause death. Cattle usually refuse to eat leafy spurge unless it is given to them in dry, weedy hay or when better forage is not available.

A conservative 1979 estimated loss in the United States of $10.5 million annually was based on expenditures for controlling leafy spurge and loss of productivity. Although leafy spurge infestations are most severe on undisturbed lands, on cultivated cropland the weed can reduce crop yields by 10 to 100%. A 1990 study conducted by North Dakota State University estimated the direct annual financial impact in Montana, North Dakota, South Dakota, and Wyoming to be $40.2 million with secondary impacts at $89 million and the potential loss of 1,433 jobs annually.